Computed Tomography (CT) is a mainstay in diagnostic imaging. It plays key roles in disease detection and characterization, and also in patient follow-up during and after treatment. Biological soft tissue consists mainly of light elements, and its density is nearly uniform with little variation. Conventional attenuation-based X-ray imaging cannot provide sufficient contrast for biological soft tissue. X-ray phase imaging is sensitive to structural variation of soft tissue and offers superior contrast resolution for characterization of cancerous and other diseased tissues. The cross-section of an X-ray phase shift image is a thousand times greater than that of X-ray attenuation in soft tissue over the diagnostic energy range. This implies that phase imaging can achieve a much higher signal-to-noise ratio and substantially lower radiation dose than attenuation-based X-ray imaging.
Grating interferometry is a state of the art X-ray imaging approach, which can simultaneously acquire information of X-ray phase-contrast, dark-field, and linear attenuation. Conventional grating interferometers often use flat gratings, with serious limitations in the field of view and the flux of photons.